In processing a substrate (hereinafter, also referred to as a wafer) in a semiconductor manufacturing process and the like performed in a vacuum, the process needs to be uniformly performed over the whole wafer in, for example, a chemical treatment chamber for performing a chemical treatment on the wafer. Accordingly, developing various technologies is required for adjusting a temperature in order to secure a uniform temperature on a surface of the wafer and for securing a uniform gas flow on the wafer.
In the related art, the following single wafer-type plasma processing apparatus has been proposed, which processes one sheet of wafers at a time. That is, a baffle plate is provided in the plasma processing apparatus so as to divide the inside of the chamber into a reactant gas introducing side and a reactant gas exhausting side. Exhaust regulating holes are formed in the baffle plate and a cross sectional area of the flow path of each exhaust regulating hole is varied depending on its position to thereby secure a uniform flow of the reactant gas. Further, a two wafer-type plasma processing apparatus provided with an exhaust plate has been proposed. The exhaust plate is disposed in the chamber such that a front surface side of a substrate is separated from a back surface side thereof. Exhaust holes are formed in the exhaust plate at predetermined distances from each other to thereby control the exhaust.
In the plasma processing apparatuses described above, however, a gas flow pattern on spots of a substrate to be processed, located in the vicinity of portions of the baffle plate where communication holes (corresponding to regulating holes and exhaust holes) are formed, is different from a gas flow pattern on other spots of the substrate to be processed, located in the vicinity of portions of the baffle plate where no communication holes are formed. Therefore, it is difficult to sufficiently secure uniformity of gas flow on the substrate to be processed.